There should be water coming out of the wet tank with no air drier.
The humidity in the air is condensed out of the air sucked in and squeezed by the air compressor.
Most of it will be collected in the wet tank, but the whole system will be humid inside.
It is that humidity that is the devil when it gets cold out.
Yes, on stopping in arctic conditions and chance of wet linings, set the parking brake, position wheel chocks on the down hill side just an inch away from the tires, go back and release the parking brake, and hope it rolls that inch against the chocks.
Works good as long as a lack of air integrity doesn't put them back on shortly...
happy coaching!
buswarrior